Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.70	5.442%	$150.4657	$150.47	$150.45	$150.50
Purchase #2	$88.59	7.290%	$95.0482	$95.05	$95.05	$95.00
Purchase #3	$195.91	7.486%	$210.5758	$210.58	$210.60	$210.60
Purchase #4	$207.90	13.384%	$235.7253	$235.73	$235.75	$235.70
Purchase #5	$216.33	8.571%	$234.8716	$234.87	$234.85	$234.90
Purchase #6	$40.65	12.193%	$45.6065	$45.61	$45.60	$45.60
Purchase #7	$183.67	9.200%	$200.5676	$200.57	$200.55	$200.60
7 purchase totals =	$1,075.75		$1,172.8607	$1,172.88	$1,172.85	$1,172.90